Integrated lead or wireless disk drive head suspensions and head suspension components are well known and disclosed in, for example, the Arai U.S. Patent Application Publication 2007/0133128, the Sone et al. U.S. Pat. No. 5,694,270 and the Klaassen et al. U.S. Pat. No. 6,608,736. These devices generally include a flexure mounted to a load beam or integrated into the suspension. A magnetic head slider is mounted to a gimbal region of the flexure. The flexure typically includes a spring metal layer and a conductor layer. The conductor layer includes a plurality of conductors or traces extending between terminal pads on opposite ends of the suspension for electrically connecting the magnetic head to disk drive circuitry. A layer of insulating or dielectric material separates the traces from the spring metal layer. A cover layer or cover coat layer may be formed on the portions of the traces opposite the insulating layer.
Subtractive and/or additive processes can be used to manufacture these devices. Subtractive manufacturing processes as disclosed in, for example, the Bennin et al. U.S. Pat. No. 5,839,193 use photolithography and etching processes to form the flexure from laminate material stock having a spring metal layer and conductor layer separated by an insulating layer. Additive manufacturing processes as disclosed in, for example, the Matsumoto et al. U.S. Pat. No. 5,666,717 use photolithography, deposition and etching processes to add the insulating layer, conductor layer and other structures to the spring metal layer.
One characteristic of integrated lead head suspension components is that the spring metal layer acts as a ground plane for the traces. For a number of reasons, including the relatively thin dielectric layer, the traces and spring metal layer can be electrically coupled. These electrical characteristics can reduce the signal performance characteristics of the traces. In addition, the area available for routing traces continues to decrease as the trend towards smaller magnetic head sliders drives smaller head suspensions and head suspension components. To compensate for spatial constraints and improve signal transmission between the magnetic head slider and disk drive circuitry, a multi layer or stacked trace configuration may be utilized.
For example, the Sone et al. U.S. Pat. No. 5,694,270, discloses a first conductor pattern formed on the suspension and flexure through an insulator layer and a second conductor pattern laminated or stacked on the first conductive pattern through a second insulator layer to accommodate reduced width flexure beam elements. In another example, the Klaassen et al. U.S. Pat. No. 6,608,736 discloses read line traces arranged on top of each other and separated by a dielectric layer to increase the data rate that can be transferred between the magnetic head and drive circuitry preamplifier. In still another example, the Arai U.S. Patent Application Publication 2007/0133128 discloses a high conductivity ground layer under portions of the write traces and separated by an insulating layer to lower the trace impedance and lower signal transmission loss.
Recent trends in hard disk drive technology require electrical and mechanical suspension characteristics that increase the bandwidth of signal transmission, decrease differential impedance of the traces and decrease stiffness in the gimbal region of the flexure. Modifying the trace configuration to optimize one of these characteristics can have negative impacts on the other characteristics. Bandwidth is directly proportional to the distance, d, separating the stacked traces. Differential impedance is directly proportional to the distance, d, and inversely proportional to the width, w, of the stacked traces. Stiffness is directly proportional to the width, w, and the square of the distance, d. Increasing bandwidth by increasing the distance, d, has a negative impact (increases) on both differential impedance and gimbal stiffness. Reducing differential impedance by increasing the width, w, has a negative impact (increases) on gimbal stiffness.
There remains a need for stacked integrated lead trace structures that provide improved electrical characteristics without negatively impacting the mechanical performance of the head suspension. To be commercially viable any such structures must be capable of being efficiently manufactured.